Remotely controlled vehicle

ABSTRACT

A three-wheeled remotely controlled vehicle is provided whose direction, speed and braking are automatically controlled by a remote transmitter. The signal from the transmitter is radiated to an electronic power control unit on the vehicle, and the power control unit causes a control to be exerted on the rear wheels of the vehicle. The front wheel of the vehicle is swivelly mounted to be freely rotatable about a vertical axis. The direction, speed and braking of the vehicle are controlled by individually controlling the rotation and direction of rotation of the rear wheels of the vehicle independently of one another.

1 ill" llnite States Patent 1191 1111 3,720,21

Frownfelter [4 1March 13, 1973 1 REMOTELY CONTROLLED VEHICLE 2,228,692 11941 Davies ..325/180 x [76] Inventor: Jerald L. Frownfelter, 1723?Minmg"; ag

$23 2 Street Granada 3,303,821 2/1967 Harris ..l80/6.5 x

[22] Filed: Feb. 16, 1971 Primary Examiner-Benjamin Hersh AssistantExaminer-John P. Silverstrim [2]] Appl' 115176 AttrneyJessup & Beecher[52] US. Cl. ..l80/6.5, 180/98, 318/587, [57] ABSTRACT 325/113, 343/225[51] Int 27/06 360k loo, 362d H24 A three-wheeled remotely controlledvehicle is pro- [58] Field 0 Search 180/98 65 318/16 581 vided whosedirection, speed and braking are auto- 318/587. 3. matically controlledby a remote transmitter. The Y signal from the transmitter is radiatedto an electronic [56] References Cited power control unit on thevehicle, and the power control unit causes a control to be exerted onthe rear UNITED STATES PATENTS wheels of the vehicle. The front wheel ofthe vehicle is 3 563 327 2/1971 Mier 180/98 x swivelly mounted to befreely rotatable about a verti- 3:011:5s0 12/1961 Reid .IIIIIIITI,"180/98 cal axis- The Speed and braking 0f the vehi' 3 039 554 9 2Hosking 6 3L", um 79 X cle are controlled by individually controllingthe rota- 3,293,600 12/1966 Gifft ....180/98 X tion and direction ofrotation of the rear wheels of the 2,766,426 /1956 Wilhelm ....l80/98 Xvehicle independently of one another. 3,053,478 9/1962 Davenport etal... ..343/225 X 3,276,019 9/1966 Fackler ..325/180 X 10 Claims, 7Drawing Figures /E/e e-fran/l': foa /er Ca/z/ra/ (/n/z) EjJZ #MAhZf/fl,

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REMOTELY CONTROLLED VEHICLE BACKGROUND OF THE INVENTION The inventionhas particular utility in conjunction with wheeled vehicles for carryingplayers clubs around a golf course, and will be described in such anenvironment. Remotely controlled wheeled golf club carriers are known,and one type of such a carrier is described, for example, in US. Pat.No. 3,472,333, which issued Oct. 14, 1969 to Hugo Loewenstern, Jr. Theprincipal objective of the present invention is to provide an improvedand simplified remotely controlled carrier of the general type describedin the Loewenstern patent.

For example, as mentioned above, the embodiment of the invention to bedescribed comprises a threewheeled, electrically propelled golf clubcarrier whose motion, speed, direction and braking are controlled by anelectronic power control unit mounted on the vehicle. The electronicpower control unit, in turn, is activated by the reception of signalstransmitted by a remote transmitter. The transmitter may be encased in aunitary housingwhich is carried by the person controlling the vehicle,and the signal radiated by the transmitter causes the carrier to followthe person.

In a constructed embodiment of the invention, for example, the golf clubcarrier is controlled to follow the person with the transmitter at adistance of from 6 to 8 feet. The vehicle enters a reverse mode andbacks up when the person approaches it within the aforesaid distance. Inaddition, on a down-slope, any tendency for the vehicle to close thedistance between it and the controlling person results in the drivemotors of the vehicle entering a reverse mode and acting as power brakesfor the vehicle.

An important feature of the vehicle and control system of the presentinvention is the mounting of the front wheel of the vehicle on a swivelmount for free rotation about a vertical axis. The vehicle is steered bythe independent forward and reverse rotational control of its rearwheels, rather than by attempting to provide any distinct steeringfunction for the front wheel of the vehicle, as is the case in the priorart systems. As the rear wheels of the vehicle of the present inventionare independently controlled by the electronic power control unit toperform the steering function, the front wheel rotates freely about theaforesaid vertical axis on its swivel mount. I

The aforesaid constructed embodiment of the invention comprises a golfclub carrier which is capable of operating on grass turf with a fullload of two golf bags There have been numerous attempts in the prior artto achieve the functions described above. However, such attempts have,for the most part, been unsuccessful both functionally and commercially.The lack of success of the prior art units is due primarily to theircomplexity, and especially due to the complexity of the front wheelsteering control in the prior art systems, and in which the steeringfunction is usually performed in reliance on the variation of signalstrength between two antennas mounted in relatively close proximity toone another.

Other problems in the prior art remote vehicle control systems havestemmed from the disadvantages of employing a multiplicity of switchesand relays for the application of predetermined increments of power tothe drive motors of most of the prior art controlled vehicles. It iswell known that such switches tend to get dirty and wear out. Also, theprior art multi-switch control is incapable of providing compensationfor unbalanced motors, or for unequal load distribution and unequalfrictional drag as might be occasioned by faulty wheel bearings or bydifference in grass structure between the wheels. Some of the prior artremote vehicle control systems, moreover, employ power rheostats whichare inherently inefficient, and which are subject to excessive heat andfrequent failures.

The objectives of the present invention, therefore, include theprovision of a driving, steering and braking control unit for a remotelycontrolled powered vehicle, and which overcomes the above-mentioneddisadvantages of the prior art systems of the same general nature.

As will be described, the vehicle in the system of the present inventionis operated by means of a remote radio transmitter encased in a smallcompact unitary housing, and the control is effectuated by means of aunique electronic control circuit having infinite resolu tion andproportional control of both forward and reverse power applied to eachof two electric motors.

The electric motors are independently coupled to and at a maximum speedof the order, for example, of

450 feet per minute. The speed of the vehicle is determined by the rateat which the player carrying the transmitting unit moves ahead of thevehicle. In other words, the vehicle moves at the speed the playerelects to walk, and it follows the player at a distance of from 6 to 8feet. Also, and as mentioned above, on a downhill slope, any tendencyfor the vehicle to close with the player is prevented by the vehicleentering a braking mode. Whenever the player carrying the transmittingunit changes the direction in which he is walking, the vehicle isautomatically controlled to alter its course and, at all times, tofollow a predetermined distance behind the player. I

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective representationof a golf club carrier constructed to incorporate the concepts of thepresent invention;

FIGS. 2 and 3 are further views of the vehicle of FIG. 1, with the bodyremoved so as to reveal the chassis, as well as the drive motors andcontrol components of the vehicle;

FIG. 4 is a schematic representation of the transmitter used in thesystem of the invention, and which is encased in a small unitary housingfor convenient hand carrying by the controlling person;

FIG. 5 is a block diagram of the electronic power control unit which ismounted on the vehicle of FIGS. 1-4, and which responds to remotesignals from the transmitter to control the vehicle;

FIG. 6 is a diagram of a motor controller which also is mounted on thevehicle and which is controlled by the electronic power control unit ofFIG. to exert the desired control on the drive motors of the vehicle;and

FIG. 7 is an electrical block diagram of the transmitter of FIG. 4.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT As shown in FIGS.1-3, the radio controlled vehicle of the invention may take the form ofagolf club carrier 10. The vehicle is constructed to carry one or morebags of golf clubs, and it is controlled to follow a player around thegolf course at a predetermined distance behind the player. The carrier10, as shown in FIGS. l-3, includes a left rear wheel 12 and a rightrear wheel 14. The carrier also includes front wheel 16 which issuspended from an appropriate swivel mount 18 for free rotationthroughout 360 about a vertical axis.

The rear wheel 12 of the carrier is driven by an electric motor M1through an appropriate chain drive 13, and the rear wheel 14 of thecarrier is driven by an electric motor M2 through an appropriate chaindrive 15. It is evident that other means may be used for mechanicallycoupling the motors M1 and M2 to the wheels 12 and 14. The electricmotors M1 and M2 are independently controlled and they operateindependently to control the speed and direction of rotation of thewheels 12 and 14. I

An electronic power control unit 20 is mounted on the carrier 10, and itincludes a left antenna 22 and a right antenna 24. The antennas 22 and24 may take the form, for example, of vertical ferrite rods, and theyare mounted on the ends of an arm 26. The antennas may be encased inappropriate plastic housings, and the arm 26 may be in the form of aplastic tubular member through which the leads from the antennas 22 and24 extend to the control unit 20. A motor controller unit 21 is alsomounted on the golf cart 10, and it responds to signals from the powercontrol unit 20 to control the motors M1 and M2.

The transmitter portion of the system may be mounted, for example, in anappropriate housing 11, such as shown in FIG. 4. The housing 11 may beof a size so as tobe conveniently carried by the controlling person. Aclip 23 may be provided to permit the unit to be carried on the belt, orby other appropriate means, as the controlling person walks around thegolf course. An on-off switch is mounted, for example, at the top of thetransmitter, so that the transmitter may be conveniently turned off bythe controlling person whenever he wishes to approach the vehicle, or tomove without the vehicle following him. As will be described, thevehicle is constructed so that it automatically enters a dynamic brakingmode, whenever the transmitter is turned off so that it comes to animmediate stop.

An appropriate electronic package 17 is mounted within the housing 11,and the package 17, as will be described, actually includes threeseparate transmitters in a particular embodiment of the system. Arechargeable battery 19 is also provided in the housing 11. The battery19 has appropriate external contacts, so that the transmitting unit maybe plugged into a receptacle on the vehicle when not in use, so that thebattery 19 may be recharged by the batteries on the vehicle. Threeseparate antenna rods 31 are also mounted within the housing at rightangles to one another. These antenna rods may be constructed ofappropriate ferrite material, and they may, for example, have a lengthof the order of one inch.

In the particular embodiment of the transmitter to be described, threeseparate oscillators are used, all of the same frequency and eachconnected to a different one of the antenna rods 31. The oscillators arethen activated in sequence, so that only one transmitter is on at anyparticular instant. In this way, a truly omnidirectional effect isachieved, and there is no need for the transmitting unit to have anyparticular orientation with respect to the vehicle for satisfactoryreception by the vehicle of the signal transmitted by the transmitterunit.

The signal radiated by the transmitter of FIG. 1 is preferably magnetic,rather than electromagnetic, so as to have a limited radiation range,similar to the signals radiated in garage door openers, or other similarremotely controlled instrumentalities. The signal from the transmitteris radiated to the vehicle, and is intercepted by the antennas 22 and24. These antennas are connected to the electronic power control unit 20which is shown in block form in FIG. 5. It should be pointed out thatthe various circuits which make up the individual blocks in FIG. 5 arewell known per se, and it is believed unnecessary to include a detailedcircuit description of the individual components herein.

The electronic power control unit 20, as shown in FIG. 5, includes adifference channel 50 and a sum channel 52. The right antenna 24 andleft antenna 22 have a first pair of inductance coils associated withthem so that signals representing the difference between the signalsreceived from both antennas are applied to the difference channel 50.The antennas also have further inductance coils associated with them, sothat signals representing the sum of the two signals received by the twoantennas are applied to the sum channel 52. The difference channel 50constitutes the channel which produces a heading error signal," and thiserror signal drops to zero, as does the difference between the signalsapplied to the pre-amplifier 54 in the difference channel 50, when theheading of the vehicle corresponds to the direction in which thecontrolling person is walking. The channel 52, on the other hand,generates a position error signal, and this position error signalchanges amplitude in correspondence with the distance in which thevehicle is from the controlling person, as does the amplitude of the twosignals applied to the pre-amplifier 56in the sum channel 52.

The three signals generated by the transmitter of FIG. 4 have a singlepredetermined carrier frequency which may, for example, be in a range of-400 kilocycles. Each group of four vehicles may, for example, beassigned a different carrier frequency, so that four adjacent vehiclesin a golfing foursome, for example, will not be erroneously controlledby each others signals.

The amplified signal from the pre-amplifier 54 in FIG. 5 is amplified ina further amplifier 58 which is of the automatic gain controlled type,and the amplified signal from the amplifier 58 is passed through afilter 60 which passes only the carrier frequency selected for theparticular vehicle-The resulting signal passed by the filter 60 isamplified in a buffer amplifier 62 and demodulated in a phase sensitivedemodulator 64. The demodulator 64 produces an output signal which is adirect current signal and which has an amplitude dependent upon theheading error of the vehicle with respect to the controlling person, andwhich has a polarity corresponding to the direction of the headingerror.

It should be pointed out that the difference signal applied to thepre-amplifier 54 is in phase with the sum signal applied to thepreamplifier 56 for a heading error, for example, to the left, and thedifference signal applied to the pre-amplifier 54 is in a phaseopposition with the sum signal applied to the preamplifier 56 for aright heading error.

The signal from pre-amplifier 56 in the sum channel 52 is applied to anautomatic gain control amplifier 66, whose output is passed through afilter 68 to a buffer amplifier 70. The filter 68, like the filter 60,selects the particular carrier corresponding to the controlled vehicle,and only that carrier is amplified by the buffer amplifier 70. Theoutput signal from the buffer amplifier 70 is passed through a limiter74. As will be described, the signal passed to a phase senitivedemodulator 72 and by the buffer amplifier 70 is actually amplitudemodulated by an appropriate tone signal which is demodulated by thephase sensitive demodulator 72. The limiter 74 serves to remove anyamplitude modulation from the carrier from the buffer 70, so that areference signal may be provided for the phase sensitive demodulators 64and 72.

The demodulator 72 produces a signal whose amplitude is actually ameasure of the amplitude of the sum signal applied to the pre-amplifier56,'and that signal is a direct current signal which is amplified by adirect current amplifier 75. The amplifier 75 produces a direct currentsignal which serves to control the gain of the amplifiers 58 and 66, sothat the sensitivity of the system will be relatively independent ofdistance between the transmitters and' the vehicle. The amplitude of thedirect current output from the amplifier 75 is a measure of the distanceof the controlling person from the vehicle, and that signal is used as aposition error signal, as will be described.

The demodulator 72 also produces the key tone which is amplitudemodulated on the signal, and that key tone is detected in a usual phaselocked tone detector 92. The direct current output from the amplifier 75is fed to a signal monitor 71, and the output from the signal monitor71, together with the output from the key tone detector 92 is applied toa relay driver 94. The relay driver 94, as will be described inconjunction with FIG. 6, controls the main power relays K1 and K2 of thesystem. The signal monitor is a threshold circuit, and it passes thedirect current signal from the amplifier 75 to the relay driver, onlywhen that signal exceeds a predetermined threshold.

The signal from the monitor 71 together with the detected key tonesignal from the detector 92 are required before the relay driver willoperate the main power relays of the system, so as to activate thevehicle control system. This means that all signals below apredetermined amplitude threshold are incapable of controlling the unit,so that it is not susceptible to spurious control by extraneous signals.Also, an overriding interference signal of the proper frequency, whichwould be passed by the filter 68 does not produce a spurious control ofthe unit, since the interference signal does not have the appropriatekey tone modulated on it. Therefore, no signal is produced by the keytone detector 92 in the presence of the overriding interference signal.This means that powerful interfering signals do not produce spuriouscontrols of the vehicle, but merely cause the main power relays of thevehicle to open. The motor controller system is constructed, as will bedescribed, so that immediate dynamic braking is provided for theelectric drive motors of the vehicle whenever the main power relays areopen.

The heading error signal output from the demodulator 64 is passedthrough a dynamic compensator 78 to a direct current amplifier 80. Thedynamic compensator 78 may be any known type of anti-hunt circuit. Alimiter 82 controls the direct current amplifier 80 so that the outputof the amplifier 80 is held below a predetermined threshold. The directcurrent output from the amplifier 75 is fed through a similar dynamiccompensator 77, and through a distance setting control potentiometer 79,to a direct current amplifier 86. The

amplifier 86 is controlled by a limiter 88 which limits its output to apredetermined value. The amplifier 80 produces the heading error signal,and the amplifier 86 produces the position error signal.

The potentiometer 79 is connected to a negative voltage source, so thatwhen the direct current output from the amplifier drops below apredetermined level, the output from the amplifier 86 becomes negative.This produces a reverse drive on the motors M1 and M2 to brake thevehicle on a downhill run, for example, or to cause the vehicle to backup, whenever the controlling person moves within a predetermineddistance from the vehicle. For example, the voltage produced by the DCamplifier 75 may range from 0 to +5 volts, whereas the potentiometer 79may be connected to a -6 volt source. Then, whenever the output from theamplifier 75 drops, for example, to a value of 2.5 volts, the DCamplifier input becomes negative as does the position error signalproduced by it.

The direct current output of the amplifier 80 is applied to a sumamplifier 84 and to a difference amplifier 90, and the direct currentoutput of the amplifier 86 is also applied to the sum amplifier 84 andto the difference amplifier 90. The outputs of the amplifiers 84 and 90are applied to power amplifiers in the circuit of FIG. 6, as will bedescribed. Whenever there is a heading error signal from the directcurrent amplifier 80, that signal is applied to the amplifiers 84 and 90with a polarity dependent upon the heading error, and with an amplitudedependent upon the amount of heading error, and with like polarity.Likewise, the position error signal from the direct current amplifier 86is applied, with opposite polarities, to the amplifiers 84 and 90, thelatter signal having an amplitude dependent upon the distance of thecontroller from the vehicle.

It will be appreciated that when the heading is proper, the headingerror signal is zero, so that the position error signal is appliedpositively to the amplifier 84 to cause the motor M1 to turn in onedirection, and is applied with opposite polarity to the amplifier 90 tocause the motor M2 to rotate in the opposite direction. when the motorsM1 and M2 are so driven, both'the wheels 12 and 14 of FIGS. 2 and 3 aredriven to move the vehicle in a forward direction. When the controllingperson moves within the predetermined distance of'the vehicle, and asdescribed above, the polarity of the position error signal reverses, sothat the wheels are driven in the reverse mode.

Should the controlling person change his direction to the right withrespect to the vehicle, a positive error signal resulting from thedirect current amplifier 80, for example, causes the motor M1 to rotatemore quickly; and causes the motor M2 to rotate more slowly, or toreverse its rotation, so that the desired turning function may beachieved. Likewise, a change in position of the controlling person tothe left of the vehicle, causes the heading error signal to be negative,so that the reverse effect is produced. In either instance, theamplitude of the heading error signal is dependent upon the amount ofheading displacement of the controlling person with respect to thevehicle.

The limiters 82 and 86 serve to limit the heading and position errorsignals, so that the heading error signal always predominates. In thismanner, when the vehicle is at a maximum distance, so that the positionerror signal is a maximum, it is never sufficiently dominant, so as tosaturate the motors M1 and M2, and cause them to be unresponsive tovariations in the heading error signal. In this way, the vehicle alwaysresponds to the heading error signals, regardless of its distance fromthe controlling person.

A switching unit 29, as shown in FIG. 3, is mounted on the vehicle 10,and it includes appropriate manual switches so that the aforesaiddynamic braking function may be removed from the motors M1 and M2 topermit the vehicle to be towed, in the event of power failure. Thevehicle carries storage batteries 27, as shown in FIG. 2, which serve toenergize the motors and which may be recharged by an appropriatecharging system when the vehicle is not in use.

The motor controller circuit of FIG. 6 responds to signals from the sumamplifier 84 and from the difference amplifier 90 of FIG. 5, and alsofrom the relay driver 94. For example, the signals from the differenceamplifier 90 are applied to a right power amplifier 100, whereas thesignals from the sum amplifier 84 are applied to a left power amplifier102. The relay driver 94 is connected to the energizing coils of a pairof main power relays K1 and K2. The armatures of the relays K1 and K2are connected to the motors M2 and M1, as shown. The motors M1 and M2are connected to the battery 27 which also are connected to the poweramplifiers 100 and 102. The batteries apply the required energizingvoltages from the motors.

When the relays are energized, the power amplifiers 100 and 102 areconnected respectively to the motors M2 and M1. However, when the relaysK1 and K2 are not energized, a short circuit is applied across thearmatures, so that appropriate dynamic braking may be realized. Theswitching 29 referred to above is connected to a dynamic brake relay K3.When the switch of the unit 29 is actuated, the dynamic brake relay K3is de-energized so as to remove the short circuit from the armatures ofthe motors M1 and M2 and, thereby, remove the dynamic braking. Thislatter control permis the vehicle to be moved, for example, by towing,in the event ofa power failure, and without the dynamic braking which isunwanted under such conditions.

The transmitter system, as shown in FIG. 1 includes three oscillators200, 202 and 204. Each of these oscillators may be tuned to generate thesame selected carrier frequency, which coincides with the frequency atwhich the particular vehicle to be controlled by the transmitter isresponsive. The oscillators are respectively coupled to the variousferrite antennas 21 referred to in conjunction with FIG. 4. Theoscillators 200, 202 and 204 are controlled by a sequence generator 206.The sequence generator 206, in turn, is controlled by a tone oscillator208, and the tone oscillator causes the sequence generator to switch theoscillators 200, 202 and 204 on and off in a sequence, and at a ratedetermined by the frequency of the tone 'oscillator.

The result is that each antenna rod 31 generates a burst of oscillationat the carrier frequency. The three antenna rods 31 are positioned atright angles to one another, as mentioned above, so that the transmitterhas effective omni-directional characteristics, and at least one of thethree signals reaches the receiving antennas 22 and 24 of the vehicle,regardless of the orientation of the transmitter unit. The receivedbursts of carrier frequency occur at the switching rate of the sequencegenerator, that is, at the frequency of the tone oscillator 208, whenall three signals are received. When one or two of the three signals isreceived, the bursts occur at a harmonic of the tone oscillator. The

key tone detector 92 of FIG. 5 responds to the fundamental or harmonicrepetition frequency to generate a signal for the purposes describedabove.

The invention provides, therefore, an improved remote control system,which is economically and functionally feasible, and which causes avehicle to be fully and automatically controlled from a remote signalsource. It will be appreciated that although a particular embodiment ofthe invention has been shown and described, modifications may be made,and it is intended in the following claims to cover all themodifications which fall within the spirit and scope of the invention.

What is claimed is:

1. A remotely controlled vehicle comprising: a chassis; a pair of wheelsmounted to said chassis; first and second reversible electric motorsmechanically coupled to respective ones of said wheels for driving saidwheels at variable speeds and in a forward or reverse direction; aforward wheel swivelly mounted to said chassis for rotation about avertical axis; a pair of antennas mounted on said vehicle at each sidethereof and spaced apart from one another for intercepting controllingsignals from a remote control source; circuit means coupled to saidantennas for producing a first signal representative of the differencein the amplitudes of the signals intercepted by said antennas and forproducing a second signal representative of the sum of the amplitudes ofthe signals intercepted by said antennas; a first electronic systemconnected to said circuit means and responsive to said first signal forproducing a direct current heading signal having an amplitude andpolarity representative of the direction of said remote control sourcewith respect to said vehicle; a second electronic system coupled to saidcircuit means and responsive to said second signal for producing adirect current position signal having an amplitude representative of thedistance of the vehicle from said remote control source; and a motorcontrol circuit coupled to said first and second electronic systems andresponsive to said direct current heading signal and to said directcurrent position signal for controlling the speed and direction ofrotation of said first and second electric motors.

2. The remotely controlled vehicle defined in claim 1, in which saidcontrolling signals from said source have a predetermined carrierfrequency, and in which said circuit means includes filter means forpassing only said predetermined carrier frequency.

3. The remotely controlled vehicle defined in claim 1, in which saidsecond electronic system includes circuitry for reversing the polarityof said direct current position signal when said remote control sourceis within a predetermined distance from said vehicle.

4. The remotely controlled vehicle defined in claim 1, in which saidmotor control circuit includes relay means for controlling theapplication of power to said first and second electric motors, and whichincludes signal monitoring circuit means coupled to said firstnamedcircuit means and responsive to said second signal therefrom forcontrolling said relay means to prevent the energization of said motorswhen said second signal is below a predetermined amplitude.

5. The remotely controlled vehicle defined in claim 1, in which saidmotor control circuit includes relay means for controlling theapplication of power to said first and second electric motors, and inwhich the controlling signals from said source include a key tone signalof predetermined frequency, and which includes key tone detector meanscoupled to said first-named circuit means for detecting said key tonesignal, and circuitry coupled to said detector means and responsive tothe detected key tone signal for controlling said relay means to preventthe energization of said motors in the absence of said key tone signal.

6. The remotely controlled vehicle defined in claim 1, and whichincludes signal limiting means in said first and second electronicsystems to limit the amplitudes of said heading signal and said positionsignal so that the amplitude of said heading signal exceeds theamplitude of said position signal for all amplitudes of said positionsignal.

7. The remotely controlled vehicle defined in claim 1, in which saidmotor control circuit includes relay means for controlling theapplication of power to said first and second electric motors, and whichincludes circuit means controlled by said relay means effectively toshort circuit said first and second electric motors to provide dynamicbraking for the vehicle when the power is not applied to the motors.

8. The combination defined in claim 1, and which includes a transmittingunit for radiating the aforesaid signals at a predetermined carrierfrequency.

9. The combination defined in claim 8, in which said transmitting unitincludes three rod-like antennas positioned at right angles to oneanother, and three oscillators respectively coupled to said antennas.

10. A remotely controlled vehicle comprising: a chassis; a pair ofwheels mounted to said chassis; first and second electric motorsmechanically coupled to respective ones of said wheels for individuallydriving said wheels; an electronic control unit responsive to signalsfrom a remote source for producing independent drive si(gnals for saidelectric motors re resenta' tive of the irection of and dlstance to satsource with respect to said vehicle; a transmitting unit at said remotesource for radiating said signals to said electronic control unit at apredetermined carrier frequency, said transmitting unit including threerodlike antennas positioned at right angles to one another, threeoscillators respectively coupled to said antennas, a tone generator, andswitching means sequentially coupling said tone generator to saidoscillators by which said oscillators are activated and de-activated insequence and at a predetermined tone frequency.

remote

1. A remotely controlled vehicle comprising: a chassis; a pair of wheelsmounted to said chassis; first and second reversible electric motorsmechanically coupled to respective ones of said wheels for driving saidwheels at variable speeds and in a forward or reverse direction; aforward wheel swivelly mounted to said chassis for rotation about avertical axis; a pair of antennas mounted on said vehicle at each sidethereof and spaced apart from one another for intercepting controllingsignals from a remote control source; circuit means coupled to saidantennas for producing a first signal representative of the differencein the amplitudes of the signals intercepted by said antennas and forproducing a second signal representative of the sum of The amplitudes ofthe signals intercepted by said antennas; a first electronic systemconnected to said circuit means and responsive to said first signal forproducing a direct current heading signal having an amplitude andpolarity representative of the direction of said remote control sourcewith respect to said vehicle; a second electronic system coupled to saidcircuit means and responsive to said second signal for producing adirect current position signal having an amplitude representative of thedistance of the vehicle from said remote control source; and a motorcontrol circuit coupled to said first and second electronic systems andresponsive to said direct current heading signal and to said directcurrent position signal for controlling the speed and direction ofrotation of said first and second electric motors.
 1. A remotelycontrolled vehicle comprising: a chassis; a pair of wheels mounted tosaid chassis; first and second reversible electric motors mechanicallycoupled to respective ones of said wheels for driving said wheels atvariable speeds and in a forward or reverse direction; a forward wheelswivelly mounted to said chassis for rotation about a vertical axis; apair of antennas mounted on said vehicle at each side thereof and spacedapart from one another for intercepting controlling signals from aremote control source; circuit means coupled to said antennas forproducing a first signal representative of the difference in theamplitudes of the signals intercepted by said antennas and for producinga second signal representative of the sum of The amplitudes of thesignals intercepted by said antennas; a first electronic systemconnected to said circuit means and responsive to said first signal forproducing a direct current heading signal having an amplitude andpolarity representative of the direction of said remote control sourcewith respect to said vehicle; a second electronic system coupled to saidcircuit means and responsive to said second signal for producing adirect current position signal having an amplitude representative of thedistance of the vehicle from said remote control source; and a motorcontrol circuit coupled to said first and second electronic systems andresponsive to said direct current heading signal and to said directcurrent position signal for controlling the speed and direction ofrotation of said first and second electric motors.
 2. The remotelycontrolled vehicle defined in claim 1, in which said controlling signalsfrom said source have a predetermined carrier frequency, and in whichsaid circuit means includes filter means for passing only saidpredetermined carrier frequency.
 3. The remotely controlled vehicledefined in claim 1, in which said second electronic system includescircuitry for reversing the polarity of said direct current positionsignal when said remote control source is within a predetermineddistance from said vehicle.
 4. The remotely controlled vehicle definedin claim 1, in which said motor control circuit includes relay means forcontrolling the application of power to said first and second electricmotors, and which includes signal monitoring circuit means coupled tosaid first-named circuit means and responsive to said second signaltherefrom for controlling said relay means to prevent the energizationof said motors when said second signal is below a predeterminedamplitude.
 5. The remotely controlled vehicle defined in claim 1, inwhich said motor control circuit includes relay means for controllingthe application of power to said first and second electric motors, andin which the controlling signals from said source include a key tonesignal of predetermined frequency, and which includes key tone detectormeans coupled to said first-named circuit means for detecting said keytone signal, and circuitry coupled to said detector means and responsiveto the detected key tone signal for controlling said relay means toprevent the energization of said motors in the absence of said key tonesignal.
 6. The remotely controlled vehicle defined in claim 1, and whichincludes signal limiting means in said first and second electronicsystems to limit the amplitudes of said heading signal and said positionsignal so that the amplitude of said heading signal exceeds theamplitude of said position signal for all amplitudes of said positionsignal.
 7. The remotely controlled vehicle defined in claim 1, in whichsaid motor control circuit includes relay means for controlling theapplication of power to said first and second electric motors, and whichincludes circuit means controlled by said relay means effectively toshort circuit said first and second electric motors to provide dynamicbraking for the vehicle when the power is not applied to the motors. 8.The combination defined in claim 1, and which includes a transmittingunit for radiating the aforesaid signals at a predetermined carrierfrequency.
 9. The combination defined in claim 8, in which saidtransmitting unit includes three rod-like antennas positioned at rightangles to one another, and three oscillators respectively coupled tosaid antennas.